单元测试没有运行Angular4

Question

我正在尝试使用Chrome在Angular 4中运行单元测试，Chrome控制台中有一些错误，不知道如何解决这个问题，看了谷歌没有找到太多帮助。 这是我得到的错误，如果有人有解决方案将受到高度赞赏。 提前谢谢。

Uncaught TypeError: fs.existsSync is not a function
    at :9876/_karma_webpack_/webpack:/node_modules/selenium-webdriver/lib/devmode.js:33
    at Object.<anonymous> (:9876/_karma_webpack_/webpack:/node_modules/selenium-webdriver/lib/devmode.js:34)
    at Object../node_modules/selenium-webdriver/lib/devmode.js (devmode.js:34)
    at __webpack_require__ (:9876/_karma_webpack_/webpack:/webpack/bootstrap 60e3023d24bd9e093b52:54)
    at Object.<anonymous> (:9876/_karma_webpack_/webpack:/node_modules/selenium-webdriver/lib/http.js:32)
    at Object../node_modules/selenium-webdriver/lib/http.js (http.js:567)
    at __webpack_require__ (:9876/_karma_webpack_/webpack:/webpack/bootstrap 60e3023d24bd9e093b52:54)
    at Object.<anonymous> (:9876/_karma_webpack_/webpack:/node_modules/selenium-webdriver/http/index.js:29)
    at Object../node_modules/selenium-webdriver/http/index.js (index.js:255)
    at __webpack_require__ (:9876/_karma_webpack_/webpack:/webpack/bootstrap 60e3023d24bd9e093b52:54)